CHECKING ALTERNATOR SYSTEM
With all electrical equipment off (except master switch) ammeter will indicate amount of charging current
demanded by battery. This amount will vary, depending on percentage of charge in battery. As the battery
becomes charged, the amount of current displayed on ammeter will reduce to approximately two amperes.
Amount of current shown on ammeter will tell immediately whether or not alternator system is operating
normally. Amount of current shown on ammeter is load in amperes that is demanded by electrical system from
alternator. As each unit of electrical equipment is switch on, current will add up. Total, including the battery,
will appear on ammeter.
The following test procedure will help in locating faulty components:
l. Ensure that airplane is positioned so that prop blast will not interfere with other operations going on
near by. Start engine and set throttle for 1000 to l200 rpm.
2. Switch on loads and observe ammeter output increase as indicated.
a. Rotating beacon - 3 to 6 amps.
b. Navigation and instrument lights (bright position) - 4 to 6 amps.
c. Landing light - 7 to 9 amps.
If alternator does not meet above indications, refer to troubleshooting chart. Follow troubleshooting
procedure outlined on chart checking each cause and isolation procedure under a given trouble before
proceeding.
Another method of testing alternator output is accomplished by connecting a lamp-bank load consisting of
8 landing lights or 3 ohm, l00 watt resistors wired in parallel from main bus (+) to airframe ground (-). (Refer
to figure 24-l.)
—NOTE—
On air-conditioned aircraft, full alternator output on ground
must be limited to not more than 10 minutes Refer to Pilot’s
Operating Handbook.
24 - 31 - 00
Page - 24 - 10
Reissued: August 1, 1986
1I9
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
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